Want a FreeBSD manpage equivalent of {spl,zfs}-module-parameters

[rincebrain]

Describe the feature would like to see added to OpenZFS

The title description is imperfect, but...

There's not really good documentation of the equivalents of various out-of-band parameters from Linux on FreeBSD.

It would be nice to make it easier for FreeBSD users to set/get various information.

How will this feature improve OpenZFS?

It would make some of these settings and information sources readily available to people who aren't so good at grepping the Linux manpages, then the source.

Additional context

This was, admittedly, inspired by the difficulty I had extracting information for helping someone debug a problem in FreeBSD on IRC, which is what resulted in me learning what I wrote in #12113.

(I'll probably take a whack at doing this during some downtime, I just wanted to file an issue and see if anyone thought it was a terrible idea before I started on it...)

(It'd be nice to have it preprocessed from a shared source of truth with the aforementioned man pages, but that would be a fair bit more work to add...)